I agree with the post by vass20. Just adding a few pics and my 2p worth.
The safety catch is easily visible and easy to understand how it works, but the main catch is hidden and not so obvious so here is a theoretical diagram of main bonnet catch :
Main catch - highlighted with red circle, spray lots of WD40 then leave to soak for about 10 minutes, then wipe off the excess WD40 and dirt with a paper kitchen towel.
The moving part of the catch (hardly visible here as it is siezed) is highlighted in red.
Spray on WD40 again.
A similar catch on a laguna, use a screwdriver (shown in blue) to move the catch several times until it moves freely and fully into position as shown in the photo.
If it will not move freely then better access to it is needed to clean and lubricate it, either from below or by removing plastic trim.
Spray on a bit more WD40 then wipe off the excess WD40 and dirt.
The catch needs to be protected and lubricated with thicker
or grease now it is freely moving. An aerosol spray grease is best as it will penetrate into the latch and remain longer than
Clean the plastic safety catch handle and surrounding area. It is possible that some chemicals may damage or deform the plastic so soapy water may be safest. Dry off well afterwards.
The safety catch metal hook is shown highlighted in red, spray WD40 and leave to soak at the hinge pin and spring attached to the bonnet bracket, and where it attaches to the plastic handle. Clean the excess WD40 and dirt off.
Spray on WD40 again.
Move the handle and catch backwards and forwards several times to remove corrosion and check it is moving freely and does not stick at any point.
Spray on a bit more WD40 and wipe off excess WD40 and apply spray grease to the metal catch. I will not advise to grease the plastic handle as it will not rust and the grease may trap more dirt or possibly affect the plastic (depending on type), it is unlikely to be harmful, but I will leave the decision to you if you feel it will be helpful or not.
If the safety catch and metal bracket fixing it to the bonnet is badly rusted, the catch is bent or will not move freely after cleaning and lubricating then it should be replaced with a new one.
Also lightly spray a bit of grease on the metal spike and rectangular hole for the safety catch.
The reason for spraying WD40 and wiping off several times is that : first time will remove dirt and sticky old grease, second (with moving the part) will loosen corrosion, third will wash off the loosened corrosion.
I also agree with vass20, instead of dropping the bonnet to lower the bonnet until the just safety catch engages (bonnet still not flush) then tug the bonnet to check the safety catch is properly engaged. Then push the bonnet down further to engage the main catch and check by tugging the bonnet again that it is secured and flush.